(1) Field of the Invention
The present invention relates generally to fluid clarification systems and, more particularly, to a system and method of determining the fraction of the various constituents resulting from the clarification system as a whole, or from one or more stages within the clarification system. The present invention is broadly applicable to systems in which solids are separated from liquids, or systems in which one liquid is separated from another liquid, or systems in which an incoming feed is split into at least two portions. However, the present invention is particularly adapted to systems for removing cuttings from drilling fluid in which the fractions of oil, water, and solids are to be determined.
(2) Description of Related Art
The present invention provides a system and method of accounting for solids and liquids at various points in a drilling mud treatment system used with a drilling rig. When an oil well is drilled, it is necessary to drill the well with drilling fluid, commonly referred to in the art as drilling mud. The drilling mud is provided to lubricate and cool the drill bit and to carry away cuttings as the mud flows upwardly in the annular flow space around the drill string. The drilling mud is pumped down the drill string to pick up the cuttings and other debris. Commonly, the drilling mud is either a water-based or an oil-based carrier.
When drilling into a high pressure formation or at great depths, safety is enhanced by incorporating a weight component, such as barium sulfate, barite, or hematite, for example, to the drilling mud to increase the weight of the drilling mud. The additives are expensive and various systems have been proposed for the recovery and recycling of drilling mud additives. Also, when drilling mud circulates through the well it picks up particles or cuttings of the earth formations cut by the drill bit. Various systems have therefore been proposed to remove the cuttings from the drilling mud so that the drilling mud can be recycled for further use in drilling operations.
Even very effective systems for removing cuttings from the drilling mud leave some mud adhering to the cuttings. For offshore drilling operations, this is particularly serious because drilling mud contains substances which are harmful to the environment, and when the cuttings are jettisoned over the side of the drilling platform, they carry deleterious substances with them into the water. Regulations in various jurisdictions around the world place strict limits on the overall quantity of such drilling mud constituents which can be discharged into the sea, and thus it is vitally important to account for all constituents of the drilling mud. It is also vital to keep track of the drilling mud, because it is a valuable commodity and every barrel of drilling mud recycled for reuse represents substantial savings to the user. Further, it is also vital to account for all the drilling mud because of the limits placed on its discharge.
Thus, there remains a need for a system which can quickly, easily, and graphically display the fractional or absolute quantities of the constituents of drilling mud. The present invention is directed to such a system.
The present invention addresses these and other needs in the art by providing a system which takes as inputs various measurements of solids and liquids in a clarification system and, from these measurements determines the various constituents and their fractional makeup within the system. The measurements may be made manually or mechanically, but in the preferred embodiment the measurements are made manually. From a quantitative analysis of easily accessible sample points, data is acquired and plugged into a spread sheet program, which numerically and graphically displays the breakdown of the constituents which make up the solids and liquids discharged from a treatment stage or of the entire system.
Thus, the present invention provides a method that resolves volumetric fractional contributions of a solids discard stream of a centrifuge or a dryer when the feed rate, volumetric fractions of the various constituents of the feed stream, and the volumetric fractional contributions of one of the constituents of the liquid discharge stream are known. The method of the invention does this based on the recognition that given a feed rate, with its given volumetric fractions, and further given one of the volumetric fractions of any constituents in the subsequent streams made up of the feed stream, there is only one solution which allows the total volumetric balance of the feed streams as compared to the subsequent streams.
Thus, in one aspect, the present invention provides a mass balance accounting system in a clarification system having at least one clarification stage. The accounting system comprises three basic elements: a means for measuring the flow rate into the clarification system; a means for measuring the constituents resulting from the clarification stage(i.e. oil, water, and solids); and an interdependent calculator to receive the measured constituents and determine the fractional contributions of the constituents from the clarification stage.
In a further aspect of the invention, a method of determining and displaying the effectiveness of the clarification system or a clarification stage is provided.
These and other features and advantages of the present invention will be apparent to those skilled in the art from a review of the following detailed description along with the accompany drawings.